The primary sources we have about the Sadducees come down to us from the Talmud, the New Testament and Josephus. The problem with these sources are each of them are adversaries to the Sadducees so we only have a one sided view. As I wrote before, I find it odd the Sadducees left no writings behind. Take a look at the history of the Church. Many heretical writings have surfaced during the last hundred years. The Gospel of Judas and the Gospel of Matthew come to mind. Why would we think the Jews are any other religion would be different?
Well, judging from what the Rabbis tell us in the Talmud, it would seem that the Sadducees were Biblical literalists, with a loose yet narrow oral tradition of practical interpretation. They seem to have greatly disapproved of the Rabbis' encouragement of a broad and deep Oral Torah, and of the move of the Rabbis to begin recording that Oral Torah in writing (to be fair, it was a relatively radical move for those days, when oral culture was still trusted and highly prized, and written literature still viewed as something of a novelty, save in rare cases where care far over and above the norms of the society was apparently taken with the text, such as in the case of the Biblical writings).
If we believe these descriptions (explicit and implicit in various narratives), then it would seem that for the Sadducees, accumulating a set of written literature outside the canon of Biblical texts was contrary to their beliefs. So unless the descriptions of the Rabbis are incorrect altogether, it seems entirely reasonable that the Sadducees left no written records of their beliefs and teachings.
